Since you are electing to go with the broken mouth, might I suggest you look for one with a myler/billy allen mouth, just to avoid the nutcracker effect compounded by the shanks. Really, a TT isn't that soft of a bit, especially since he doesn't go on loose reins yet. Does he neck rein? If not, I certainly wouldn't put him in a TT. But then again, that is just MHO. If you have tried it and he does well, then don't change him up.
Not getting on your butt here, just trying to help figure out what would work best for Bear. Also, the shorter the shanks are, the milder it will be. Billy Allen Bits
I really like the one with the gold chevrons about 1/3 the way down, if only the shanks were shorter.